Science & nature · Evidence-backed
Clavicle (Collarbone) - Structure and Function
The clavicle is the only long bone in the body that lies horizontally. It is the first bone to begin ossification in the fetus and one of the last to complete growth. Common injuries include fractures from falls or direct impacts to the shoulder.
The clavicle, or collarbone, is a long, slender bone that connects the arm to the torso, forming part of the shoulder girdle. It serves as a strut between the scapula and sternum, protecting underlying neurovascular structures and serving as an attachment site for muscles. Its S-shape provides flexibility and range of motion to the upper limb.
S-shaped curvature and orientation
The clavicle has a characteristic S-shape when viewed from above, curving laterally. It is the only long bone in the human body that lies horizontally, connecting the upper limb to the axial skeleton via the sternum. This orientation allows it to act as a strut for the shoulder girdle.
Articulation with scapula at acromioclavicular joint
The lateral end of the clavicle articulates with the acromion process of the scapula to form the acromioclavicular (AC) joint. This joint is crucial for shoulder movement and stability, linking the upper limb to the trunk and allowing a wide range of arm motion.
Articulation with sternum at sternoclavicular joint
The medial end of the clavicle articulates with the manubrium of the sternum to form the sternoclavicular (SC) joint. This is the only bony connection between the upper limb and the axial skeleton, providing the foundation for shoulder girdle movement.
Protection of underlying neurovascular structures
The clavicle lies directly over the subclavian vessels and the brachial plexus. Its position offers a degree of protection to these vital neurovascular structures as they pass from the thorax into the upper limb.
Attachment site for major shoulder muscles
The clavicle serves as an important origin and insertion point for several key muscles, including the deltoid, pectoralis major, and sternocleidomastoid. These muscles are essential for arm elevation, breathing, and neck movement.
Ossification timeline in development
The clavicle is the first bone to begin ossification in the developing fetus, typically starting around the 5th to 6th week of gestation. It is also one of the last bones to complete its growth, typically finishing in the early twenties.
Common fracture site due to its position
Because of its superficial location and role in protecting the arm, the clavicle is the most frequently fractured bone in the body. Most fractures occur in the middle third of the bone, often resulting from a fall onto the shoulder or an outstretched hand.
Non-articulated middle segment
The shaft of the clavicle has no articular surfaces; it is a non-jointed segment that provides structural length and leverage. Muscle forces and ligamentous attachments along its length enable movement at the jointed ends.
Variations in sex and population
Male clavicles are typically longer, thicker, and more robust than female clavicles. Population-level differences also exist, with variations in angle and length observed across different ethnic and geographic groups.
Nerve and vessel landmarks
The clavicle serves as a reliable anatomical landmark for locating the subclavian artery and vein, as well as the roots of the brachial plexus. Surgeons and clinicians use its borders as reference points for regional blocks and vascular access.
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